DART's LNG Bus Fleet Final Results
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AlternativeAlternative ENT OF TM EN R E A R FuelFuel P G E Y D U A N Transit Buses C I I T R E D E M ST A AT ES OF Produced for the U.S. Department of Energy (DOE) by the National Renewable Energy Laboratory (NREL), a U.S. DOE national laboratory 35th St. Craig Ave. Craig Colucci Pkwy. DART’sDART’s LNGLNG BusBus FleetFleet FinalFinal ResultsResults Alt Blvd. D ALLAS AREA RAPID TRANSIT’S (DART) LNG BUS FLEET: Final Results Alternative Fuel Transit Bus Evaluation by Kevin Chandler, Battelle Paul Norton, National Renewable Energy Laboratory Nigel Clark, West Virginia University October 2000 The authors wish to acknowledge the help and cooperation of the staff, in particular Rocky Rogers and Darryl Spencer, at the host site, Dallas Area Rapid Transit. The authors also acknowledge the editorial contri- butions of Vincent Brown at Battelle and Stefanie Woodward at NREL. World Wide Web: http://www.afdc.doe.gov National Alternative Fuels Hotline: 1-800-423-1DOE Notice This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, com- pleteness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or ser- vice by trade name, trademark, manufacturer, or otherwise does not neces- sarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Available electronically at http://www.doe.gov/bridge Available for a processing fee to U.S. Department of Energy and its contractors, in paper, from: U.S. Department of Energy Office of Scientific and Technical Information P.O. Box 62 Oak Ridge, TN 37831-0062 phone: 865.576.8401 fax: 865.576.5728 email: [email protected] Available for sale to the public, in paper, from: U.S. Department of Commerce National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 phone: 800.553.6847 fax: 703.605.6900 email: [email protected] online ordering: http://www.ntis.gov/ordering.ht ii Final Results Alternative Fuel Transit Buses Table of Contents Executive Summary . .v Overview . .1 Alternative Fuel Projects at DOE and NREL . .2 The Transit Bus Evaluation Project . .2 Host Site Profile: Dallas Area Rapid Transit . .2 DART’s LNG Buses . .3 DART’s Involvement in Air Quality Improvement . .5 Project Design and Data Collection . .5 DART’s Facilities and Bulk Fuel Storage . .7 Project Start-Up at DART . .9 LNG Engine Issues . .9 Range and Fuel Gauge Issues . .9 Other Fueling Issues . .10 Evaluation Results . .12 Bus Use in Transit Service . .12 Average Speed . .13 Monthly Miles Driven . .13 Fuel Economy, Maintenance, and Costs . .14 Fuel Economy . .14 Fuel Cost per Gallon . .15 Fuel Cost per Mile . .15 Engine Oil Consumption and Cost . .15 Factors Affecting Maintenance Costs . .16 Maintenance Costs by Vehicle System . .16 Roadcalls . .18 Warranty Costs . .18 Overall Maintenance Costs . .19 Overall Operating Costs . .19 Emissions Testing Results . .20 LNG Technology Progress in Transit . .22 Roadcalls . .23 Maintenance Costs . .23 Fuel Economy . .24 Emissions Testing Results . .24 Summary . .25 Summary and Conclusions . .26 Future LNG Operations at DART . .27 Contacts . .28 References and Related Reports . .29 Appendix A. Fleet Summary Statistics . .31 Appendix B. Emissions Test Results . .37 iii iv Methods Data were gathered daily from fuel and maintenance tracking systems for more than 1 year. The data parameters included • Fuel consumption • Mileage and dispatching records • Engine oil additions and oil/filter changes Executive Summary • Preventive maintenance action records In 1998, Dallas Area Rapid Transit • Records of unscheduled maintenance (DART), a public transit agency in Dallas, (such as roadcalls) and warranty repairs Texas, began operating a large fleet of heavy-duty buses powered by liquefied The data collection was designed to natural gas (LNG). As part of a $16 mil- cause as little disruption for DART as lion commitment to alternative fuels, possible. The original evaluation fleets DART operates 139 LNG buses serviced consisted of 10 LNG buses and 5 similar by two new LNG fueling stations. diesel buses. Five additional LNG buses were added to the evaluation after the The U.S. Department of Energy (DOE) Office start-up period. of Heavy Vehicle Technologies sponsored a research project to collect and analyze data Results on the performance and operation costs of Some early start-up issues required 15 of DART’s LNG buses in revenue service, the LNG buses to operate on restricted compared with the performance of 5 diesel routes and schedules, but after these buses operating on comparable routes. issues were resolved, the LNG and diesel fleets performed the work DART Objective expected during the evaluation period. The objective of the DOE research project, managed by the National Renewable Energy The LNG buses emitted less nitrogen Laboratory, was to provide transportation oxides and particulate matter than the professionals with quantitative, unbiased diesel buses. By most other measures of information on the cost, maintenance, oper- operation, the diesel buses performed ational, and emissions characteristics of LNG better than the LNG buses. The LNG as one alternative to conventional diesel buses had lower energy equivalent fuel fuel for heavy-duty transit bus applications. economy, higher fuel costs per mile dri- ven, and higher engine and fuel system In addition, this information should benefit maintenance costs per mile driven than decision makers by providing a real-world the diesel buses. account of the obstacles overcome and the lessons learned in adapting alternative Overall, the operating cost comparison fuel buses to a transit site previously was mixed. The operating costs for designed for diesel buses. It also identi- the original LNG buses averaged about fies technology areas where future 3% higher than for the diesel buses. research and development efforts should The 10 original LNG buses averaged be focused. The field study at DART was $0.799 per mile, and the diesel buses part of DOE’s ongoing Alternative Fuel averaged $0.773, giving the diesel Transit Bus Evaluation Project. buses an advantage of $0.026 per mile. v Alternative Fuel Final Results Transit Buses However, the new LNG buses showed wastegate). Some engine problems with the lowest operating cost per mile, the DART LNG buses persisted through at $0.713—about 8% less than the the end of the study period. Design diesel buses. work continues on the LNG buses. Lessons Learned The original LNG buses were designed with a three-tank system that provided The LNG bus evaluation project provided a range of only 250 miles in service DART, DOE, and other participants the (277 miles in track tests), well below opportunity to learn many lessons about DART’s goal of 400 miles. At DART’s alternative fuels: request, the manufacturer, NovaBUS, • Transit agency employees should learn added a fourth LNG tank, which all they can about potential problems provided an acceptable range of with alternative fuels in field opera- 358 miles in service (380 miles in tions. Agencies should plan for unex- track tests). pected contingencies and exercise patience through the start-up process. Other obstacles overcome included ensuring full tanks at each fueling stop, • Critical vehicle systems should undergo redesigning the LNG fueling nozzle to engineering design validation and/or prevent leaking, exploring the use of a performance tests before vehicles are breakaway hose to prevent damage from put into service. driveaways during fueling, and a starter • Transit agencies need to be committed lockout switch at the fueling door. to success and to invest the personal energy, infrastructure, and financial By spring 2000, DART had resolved resources needed to make alternative nearly all the problems with the LNG fuel programs work. buses by applying the lessons learned • The LNG industry needs to improve its from start-up and by cooperating with own technology support infrastructure, manufacturers and component suppli- and be able to respond to the needs of ers. The LNG buses have operated on large fleets of LNG vehicles. all routes (except a few of the longest) originating from the Northwest facility. • All critical systems need to be inte- grated through strong communication Future LNG Operations at DART and accurate information within the transit agency. DART’s two facilities for fueling and servicing LNG buses have room to Obstacles Overcome grow. New procurements for buses have a provision for LNG buses. DART Early in the deployment of the LNG continues to evaluate the operation of buses, DART experienced problems with its LNG fleet. operating range, fuel mileage, fuel filling, and reliability. DART also resolved prob- DART continues to work on optimizing lems with methane sensors, fire suppres- the LNG bus operations. DART is sion systems, electronics, and multiplex- working with Cummins and ZF (the ing systems. (Some of these problems transmission vendor) to raise the fuel also occurred with the diesel fleet.) economy 5%–10% by optimizing the shift points of the transmission and by Cummins resolved several problems improving engine component design. with early failure of engine components DART is also working to optimize the (e.g., turbocharger, spark plugs, and onboard LNG fuel tank system. vi Final Results Alternative Fuel Transit Buses Overview What Is LNG Fuel and How Is It Processed? Dallas Area Rapid Transit (DART), a transit agency based in Dallas, Liquefied natural gas is a naturally occurring mixture of hydro- Texas, has been operating lique- carbons (mainly methane, or CH4), that has been purified and fied natural gas (LNG) buses condensed to liquid form by cooling cryogenically to -260°F (-162°C).